The dancing northern lights glowing in the night sky this Labor Day weekend treated skywatchers in places like Alaska and Canada to a rose-tinted streak amidst the dazzling display. This pink-ish ribbon isn’t an aurora but it’s STEVE!
STEVE, the acronym for the Strong Thermal Emissions Velocity Enhancement, is a dazzling and colorful celestial phenomenon that was first spotted in 2016. Scientists have observed the particles associated with STEVE for decades, but they witnessed the actual phenomenon in the sky only recently. This summer, a research team directed by University of Calgary researcher D.M. Gillies confirmed that, in spite of its colorful appearance, STEVE isn’t a type of aurora but an entirely unique phenomenon.
This May, researchers endorsed that STEVE is not an aurora. The new research expands our understanding of the bizarre phenomenon even further.
Study co-author Don Hampton, a researcher at the University of Alaska Fairbanks, said in a statement, “The big thing is, we can clearly say now it’s [a] not regular aurora. It’s a new phenomenon; that’s pretty exciting.”
One characteristic that clearly distinguishes STEVE is its mauve hues, which are completely different from the characteristically green, purple, blue and yellow beams of auroras. Moreover, STEVE is visible from latitudes much farther south than auroras habitually are.
The researchers built a spectrograph at the Geophysical Institute at the University of Alaska Fairbanks and used it to study the light coming from STEVE on April 10, 2018, at Lucky Lake in Saskatchewan, Canada. They investigated its emissions to determine its wavelengths, patterns, and other properties. A spectrum serves as an identifier, so by determining STEVE’s spectrum, the team expects to further understand and categorize the novel phenomenon.
“We need to understand what the spectrum looks like and therefore understand the physics behind it,” Hampton said in the statement.
Green optical structures, frequently described as “picket fence” structures because of their typical shape, can be seen projecting through STEVE at lower altitudes, and by studying the wavelengths of the emissions from STEVE and these greenish structures, the team discovered that the green emissions have a much different spectrum from STEVE.
The team concluded that the green columns which appear along with STEVE are caused by particle precipitation, which happens when energetic particles such as electrons, protons, neutrons, and ions get accelerated through the atmosphere. This makes these green streaks a kind of aurora which is very similar to a typical auroral structure. However, owing to their very different spectrum, STEVE is in a category of its own, the researchers determined.
The study that was published in a study in the journal Geophysical Research Letters, revealed that STEVE isn’t caused by particle collisions in the atmosphere but from some sort of warm atmospheric emission.
Hampton said in the statement, “When we looked at the spectrum of STEVE, it had none of those distinct wavelengths … Instead, it’s a very broad band of light. When you turn your electric stove on, those coils get red hot, right? If you look at it with a spectrograph, you would see broadband emissions … So this is like very, very warm atmosphere emissions of some sort.”
Scientists will continue to examine STEVE in a bid to find what exactly it is and what causes it. Decoding STEVE is more than just a significant scientific pursuit as such phenomena occurring in the atmosphere can possibly disrupt radio communications between spacecraft and humans back on Earth. Thus, understanding the mechanism behind this strange, pink phenomenon could have immediate, practical applications.